A hybrid vehicle includes a transmission having different gear ratios that may be selected during a drive cycle. The vehicle may further include a torque converter coupled between the power-producing elements and the transmission. Operation of the vehicle powertrain may use various speed and torque signals. For example, sensors may provide rotational speed values for the power-producing elements. The speed sensor signals may be used for controlling the powertrain. In the event of an unavailability or loss of any of the signals, the vehicle powertrain may be disabled.